As part of a larger plant upgrade, Savin Engineers was responsible for the evaluation and design of the gas mixing system for three 100-foot diameter sludge digesters. The mixing system evaluation compared upgrading the existing bottom diffusers and retrofitting the digesters with various gas recirculation and mechanical mixing systems. A gas piston system was chosen for design based on life-cycle costs, effectiveness, and Implementability.

The retrofit consisted of installing five new gas compressors and associated piping, safety appurtenances and electrical systems including instrumentation, motor control centers and control panels. Savin was also responsible for cleaning the digesters and insulating the sidewalls and roofs. The modifications are expected to reduce total annual cost and ensure compliance with state and federal regulations for pathogen reduction.